Hello all - I may be able to answer some of your questions - I am a Purser and a trainer at BA so will try to answer any questions you have and give you an honest - balanced view of what goes on and what you can expect.
So Tilly666 I'll start with you.
Take home on EFLHR you looking at averaging as a junior £1100 - £1500 p.m (more if you do over time - however the idea of employing to stop this). EFLGW £1000 - £1300.
Rosters - EFLHR and EFLGW both work on a seniority based bidding system, as a new entrant you should expect around 40% satisfaction. So if you priority is cash and you want 3-4 day trips you might get 1 (2 maybe). Again, in relation to nightstops, you can bid for a lifestyle and bid for there and backs - but there is no guarantee you will get them if there is a surplus of trips or visa versa.
Summer months are where all the cash lies and at EFLGW Juniors have been working their arses off doing lots of nightstops as more trip[s have been available and manpower is tight, earning £1400 - £1500 because of it. However in the winter you are not realistically going to get near that as more senior people will be getting what trips there are to have.
Oh...and as for longhaul - forget it!! Unless the ad offers you direct entry into it you will be waiting years for it!
Hope this answers your questions. As I've said if you do have more I will try to answer as best I can.